1. Field of the Invention
The present invention relates to a dielectric lens apparatus employing a solid dielectric. More particularly, the present invention relates to a dielectric lens apparatus for use in a high frequency band.
2. Description of the Related Art
FIG. 3 shows a conventional typical dielectric lens 1.
A dielectric lens 1 has a curved surface 2 which is formed into, for example, a convex surface. Such a dielectric lens 1 functions to refract radio waves 3 which enter from the curved surface 2 side so they converge at a focal point 4.
However, a dielectric lens 1 such as that shown in FIG. 3 has the following problems.
First, the radiation directivity of the radio waves 3 is determined substantially by the shape of the dielectric lens 1 and the dielectric constant of the dielectric which forms the dielectric lens 1. For this reason, the dielectric lens 1 arranged as shown in FIG. 3 has only a small degree of freedom concerning radiation directivity, and so it is relatively difficult to control radiation directivity.
Also, since the focal point 4 is positioned outside the dielectric lens 1, if an obstacle is present between the dielectric lens 1 and the focal point 4, as a matter of course, the radio waves 3 will be shielded, causing the dielectric lens 1 not to function as a lens.